1. Technical Field
This disclosure relates generally to a blade outer air seal for a gas turbine engine and, more particularly, to a cooled blade outer air seal.
2. Background Information
A typical section of a gas turbine engine includes a blade outer air seal (or shroud) disposed between the blades of a rotor stage and an engine case. During operation of the engine, the blade outer air seal (BOAS) is typically subject to high temperatures induced by extremely high core gas temperatures. To maintain part integrity, BOAS are often cooled with air bled from a compressor section of the engine. In some instances, the BOAS are internally cooled by directing cooling air through a plurality of internal passages, and exiting that cooling air in a manner such that it is injected substantially radially into the core gas path. This type of cooling is useful in some applications, but is relatively inefficient in others. In other instances, the cooling apertures are oriented at a shallow angle relative to the core gas path surface of the BOAS, and include a diffuser region contiguous with the core gas path. The angled orientation and diffuser portion facilitate the formation of a protective layer of cooling air traveling along the core gas path surface of the BOAS. If the blade tips engage (i.e., “rub”) the BOAS, however, the result of this engagement can compromise the ability of the aforesaid cooling apertures to adequately cool the BOAS.